WEDNESDAY was a busy day, and a typical one, for Ian Walke. A call had come into the city’s Administration for Children’s Services, where he is a supervisor, reporting that a child in his district was going to bed hungry and maybe being hit.

Mr. Walke, a 47-year-old Trinidadian who has been with the agency for 19 years, has handled enough such calls to recognize the first questions to be asked: Is someone also hitting the mother? Is someone in the home abusing drugs or alcohol? Is someone mentally ill? People can’t know, he said, who or what is behind an apartment door until they show up and knock.

The work is in his blood, Mr. Walke said near the end of a long day with the case, one of dozens that his team of six caseworkers handles. But getting through the day, let alone staying for 19 years, takes bravery, and the people running the agency believe that everyone considering such a career should know this. Mr. Walke, as it happens, is the public face of such courage, his image gazing out from behind the words “Are you brave enough?” in new ads in the subways.

The ads are part of a campaign aimed at recruiting caseworkers each year to replace all those who depart, having decided that the stressful, chronically maligned and often underappreciated work is not for them. In each of the past two years, one-sixth of the caseworkers left, according to the agency.

“Are you cool enough?” the ads ask. “Are you smart enough?” “Are you tough enough?” With each slogan is an image of an agency employee, who seems to be waiting for an answer.

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The campaign continues through next month. The agency, which had never recruited through subway ads, said that in March it received more than twice as many job inquiries as in a typical month. The push is part of the agency’s efforts to keep caseloads manageable by retaining employees and hiring people who know what they’re getting into. “We really looked at ourselves head-on and said, we have a number of staff that we hire that do not stay very long,” said Jan Flory, deputy commissioner for the agency’s Child Protection Division. “That is harmful to our other staff, and to the work that we do.”

One reason for the attrition is added pressure since the death in January 2006 of Nixzmary Brown, a 7-year-old victim of abuse. High-profile cases lead to increased publicity, raise public awareness of abuse and produce more complaints of abuse, which in turn increase individual caseloads and put stress on the system.

Faye Moore, a vice president of Local 371 of the Social Service Employees Union, which represents child protective specialists, said last week that individual caseworkers can be made scapegoats. “What they don’t tell you in the ad,” Ms. Moore said, “is that when something goes wrong, you are basically standing there alone.”

Ms. Flory disputed the charge and said the agency valued its employees and appreciated the difficulty of their jobs.

Marie Vilus, a supervisor at the agency, said that when she started as a caseworker in the 1990s, she felt taken by surprise at the emotional toll of the job. What made the job tolerable and ultimately rewarding, she said, was the camaraderie with more experienced caseworkers, who taught her to love her clients. “You’ve got to love them first,” she said. “You’ve got to understand them first in order to deal with them on a daily basis.”

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Ms. Vilus has worked more than 12 years in a field where burnout and cynicism can creep up far too quickly. In the new campaign, she is the face of the question “Are you wise enough?”

She and Mr. Walke speak of children from old cases, now grown, returning to express thanks — for separating them from a drug-addicted parent, perhaps. And for all the complexities that can attend an investigation, Mr. Walke said, things get easier for him once he can start a conversation.

“The one level that I meet you on is, you’re a human being,” he said. “This person is not the alcohol, this person is not the drug, this person is not their criminal past. This person might have caused a mark on a child, but this is a real person you’re talking to.”